AP Chemistry
1.4 Composition of Mixtures
1.3 Elemental Composition of Pure Substances
1.1 Moles and Molar Mass
A student determines the mass percentage of copper in an impure brass alloy that contains copper, zinc, and an insoluble inert silicate impurity. The student measures a sample of the alloy, dissolves the metallic components in acid, filters and dries the insoluble impurity, and quantitatively precipitates all dissolved copper as pure, dry copper(II) oxide, \(\text{CuO(s)}\). The data collected during the experiment are shown in the table below.
Given that the molar mass of \(\text{Cu}\) is \(64.0\text{ g/mol}\) and the molar mass of \(\text{CuO}\) is \(80.0\text{ g/mol}\), what is the mass percentage of copper in the original brass sample?
| Measurement | Mass (g) |
|---|---|
| Mass of empty weighing dish | \(12.50\) |
| Mass of weighing dish \(+\) brass sample | \(16.50\) |
| Mass of dry filter paper | \(0.80\) |
| Mass of filter paper \(+\) dried insoluble impurity | \(1.60\) |
| Mass of empty watch glass | \(22.00\) |
| Mass of watch glass \(+\) dried \(\text{CuO(s)}\) | \(25.00\) |
Given that the molar mass of \(\text{Cu}\) is \(64.0\text{ g/mol}\) and the molar mass of \(\text{CuO}\) is \(80.0\text{ g/mol}\), what is the mass percentage of copper in the original brass sample?
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